Electroluminescent panel for clock radio sets



April 25, 1967 J. w. KELso 3,316,435

ELECTROLUMINESCENT PANEL FOR CLOCK RADIO SETS Original Filed June 27, 1960 wqalnlgvlmmuvnunnlll Inl United States PatentOce 3,315,435 Patented Apr. 25, 1967 3,316,435 ELECTRGLUMINESCENT PANEL FOR CLOCK RADIO SETS .lames W. Kelso, Pacific Palisades, Calif., assignor to Packard-Bell Electronics Corporation, Los Angeles, Calif., a corporation of California Continuation of abandoned application Ser. No. 38,867, .lune 27, 1960. This application Dec. 23, 1963, Ser.

5 Claims. (Cl. 313-108) This is a continuation of copending application Ser. No. 38,867, filed June 27, 1960, by IamesW. Kelso for Illuminated Indicator, now abandoned.

The present invention relates to indicator panels and, more particularly, to illuminated indicator panels for clocks, clock radios and the like.

Indicator panels are conventionally illuminated by bulbs or radium on particular portions of the panel. For example, for clocks and watches, it is conventional to paint the numerical designations and the hands of the clock with a radium composition so that the time may be readily determined in the dark without external illumination. Recently, electroluminescent panels have been developed which provide a uniform glow in the dark due to the excitation between a layer of phosphorous and a metallic layer forming the active components of such panels. This type of illumination is highly attractive for use in indicator panels but the phosphorous can be dyed to provide only a few particular colors. For example, a metallized appearance cannot be provided by dyeing the phosphorous layer. Metallized appearances are highly desirable for use in many different control panel applications because of their rich and aesthetically attractive appearance to the consumer. The consumer demand has, accordingly, prevented the widespread 'adoption of electroluminescent panels.

v In addition to the design consideration, electroluminescent panels are quite brittle and many crack or shatter when they are sheared to the required panel size., The high rejection rate materially affects the cost of electroluminescent panels. Further, due to their brittleness, indicator panels made of electroluminescent panels are delicate and crack in the presence of shock or substantial vibrations. For these additional reasons, electroluminescent indication panels are not utilized for relatively inexpensive and rugged competitive items such as clocks or radios.

In a specic illustrative embodiment of this invention, a luminous panel is provided for a clock which has a metallized appearance during the day and a predetermined color during the night. The change in appearance with the change in light conditions is quite attractive. The panel includes an electroluminiscent plate which provides for a color glow in accordance with the magnitude and frequency of the exciting potential applied thereto. The phosphorous layer side of the plate is covered with a Mylar sheet which has been vacuum plated with aluminum. The Mylar is adhered to the face of the electroluminescent plate before shearing standard manufacturing sizes to the required dimensions for the indicator panel. The Mylar is flexible and quite strong so that it protects the fragile plate during shearing to sharply reduce the number of rejects during manufacture. Further, the combined panel is relatively insensitive to the usual shocks experienced by clocks and radios in home use. Utilizing decals or masking during the vacuum plating, the desired designations can be imprinted on the Mylar.

Features of this invention relate to the provision of a rugged flexible electrically insulator member on the electroluminescent plate. .The Mylar serves as the insulator member. The Mylar reduces the light transmission from the plate but because it also serves as an insulator member greater potentials and frequencies may be .utilized to excite the plate so that greaterarnounts of light are emitted.

Further advantages and features of this invention will become apparent upon consideration of the following description when read in conjunction with the drawing wherein:

FIGURE l is a pictorial view of a clock radio utilizing the illuminated indicator panel of this invention;

FIGURE 2 is an exploded pictorial view of the illuminated indicator panel of this invention;

' FIGURE 3 is a sectional view through the electroluminescent .plate utilized in the illuminated indicator panel of this invention; and v FIGURE 4 is an enlarged fragmentary sectional view of the luminescent plate shown in FIGURE 3.

Referring to FIGURES l through 3, a clock radio 10 is provided having a radio indicator panel 11 and a clock indicator panel 12. Each of the panels 11 and 12 may include a number of numerical indications. The indicator panel 12 illustratively includes the numbers 3, 6, 9 and 12 and small circles at the other eight conventional clock positions. The panel 12 has a metallized appearance divided into four rectangular areas 13 through 15, inclusive. The areas 13 and 15 have a darker appearance than the areas 12 and 14.

As is hereinafter described, the panel 12 has the metallized appearance during daylight conditions but in the dark it glows with a predetermined color. Positioned in front of the panel 12 are a second hand 18, a minute hand 19, an hour hand 20 and an alarm set hand 21. These hands are mounted on a number of concentric shafts 34 extending from a face plate 32 of a clock mechanism 36 in the clock radio 10. The clock mechanism 36 may be conventional. The hands 18 through 21 are illuminated in the dark by the light from the panel 12.

The panel 12 includes an electroluminescent plate 25 which is electrically excited by introducing an A.C. potential from a plug 31 to two terminals 40 and 41 extending from the plate 25. rl`he concentric clock shafts 34 are inserted through a hole 26 in the plate 25. As illustrated particularly in FIGURE 3, the plate 25 includes a thin phosphor layer 2S and a metallic layer 29 sandwiched between two` ceramic layers 27 and 30. The layer 29 may be made of copper or aluminum or other conductive materials. The two terminals 40 and 41 are electrically coupled respectively to the layers 28 and 29. When the layer 28 is negative with respect to the layer 29, the interaction between the two layers causes the phosphor layer 28 to be excited and glow. The ceramic layer 27, which may be fired silica, is transparent so that a uniform glow is provided throughout the layer 27.

The particular color emitted by the electroluminescent plate depends upon the magnitude and frequency lof the signal introduced between the layers 28 and 29. Illustratively, at 20 Volts and 60 cycles, the glow is red. The level of illumination is relatively low so that the red glow or illumination is not visible during the day or when relatively high level light conditions exist. The metallized appearance provided by the panel 12 at the front of the clock radio 11 is not accomplished by the electroluminescent plate 25. A sheet 22 of strong, flexible and trans- Vsmall amount determined by the shearing angle.

it may be riveted `to the plate 25. Utilizing the adhesive v is preferred to avoid the necessity of punching holes in the plate 25 which is quite brittle. The plate 25 is-thin,

illustratively, only 0.050 inch thick. The plastic sheet 22 is afiixed to the plate 25 before the plate 25 is cut to size. The manufacturing dimensions for the plates 25k may be 7 inches by 14 inches and the desired panel size may be 4 inches -by 4 inches. A plastic sheet22 of approximately 7 by 14 inches is, accordingly, first aflixed to the plate 25 and then the laminated components are sheared to size. The plastic'sheet 22 Vmaterially reduces any cracking or splintering of the thin plate 25 when it is shcared to size.

The plastic sheet V22 is vacuum plated .before it is Vaffixed lto the plate 25. The vacuum plating deposits metal particles on the sheet 22 to give it a metallized appearance. Illustratively, the particles may be aluminum. The four areas 13 through 16.0f the plastic sheet 22 are formed by regulating the amount and pattern of aluminum deposition on the sheet 22. The areas 13 and 15, which are darker than the areas 14 and 16, have greater amounts of metallic deposition. The metallic deposition may be on the front face of the sheet 22. The sheet 22 defines a central opening 17 for the concentric clock shafts 34, and the back of the sheet 22 ,is adhered tothe plate 25.

The plate 22 reduces the transmission of light from the plate 25 for any particular exicting potential. plate 22, however, is madek of an electrically insulating materialso that larger potentials may safely be introduced to the plate 25. The'amount of light emitted from the citing potential. The resultant amount of light through the plastic sheet 22 may, accordingly, be adjusted to be the same asV the amount of light safely provided by the plate 25 without an insulator sheet 22. :r

The phosphor layer 28 may be dyed to any one of a few colors so that the color possibilities of the plate 25 alone are limited. The sheet 22, however, can be made any color so that Vthe design possibilities are materially increased. During the day, the panel12 has a metallized appearance as the illumination is not detectable; In the dark, the panel 12 changes colorsy in accordance with the phosphor dye or coloring of the sheet'22.y The desig-` nations on the sheet 22 may be provided by a silk screening, lithographie or printing operation.k

In addition to increasing the color design possibilities,

y the sheet 22 also. increases the shapepossibilities because Vit can be embossed or debossed and because it is exible. Y The plate. 25 does not have these characteristics.

at platesl 25 at an angle to each other can, accordingly,

be afiixed to the same Mylar sheetv bent at the junction between thetwo plates. An effective curved luminescent surface is accordingly provided.

As described above, the sheet 22 functions to reduce the overall brittlenessof the panel 12. ,As illustrated in FIGURE 4, the ylaminated panels 12 may be sheared at an angle. The plastic sheetv 22 extends to the left by a When the panel 12 is mounted in the clock radio10, thel edge of the panel 12 having the extending sheet 22 is faced downward.- The plate 25 is, accordingly, not in contact with the support, not shown, in the clock-radio 10 for the panel 12.y Alternatively, or in addition thereto, four mounting bolts 38 may be inserted into the plate 25 before the sheet 22 is adhered thereto. The heads" of the bolts are, accordingly, not readily visible from the yfront of the panel 12. The plastic sheet 22 serves the additional function of protecting the brittlev plate 25 frombreakage due to shocks. Y

The

Two

Y plate 25 depends partially upon the magnitude kof the ex- 4. The sheet 22 may be integral with the plate 25 by first Vacuum plating directly on the electroluminescent vplate 25. By vacuum plating directly on the plate 25,

kby the scope of the appended claims.

What is claimed is:

1. An indicator panel, including,

an electroluminescent panel having ,a phosphor layer, a metallic layer having one side positioned against one side of the phosphor layer, a first transparent ceramic layer against the other side of the phosphor layer, and a second transparent ceramic layer against the other side of the metallic layer,

v a metallized vacuum plated flexible sheet of plastic against said first transparent layer and with the sheet of plastic including indicia,

means for adhering said sheet of plastic to said first ceramic layer to prevent the electroluminescent panel from cracking, and

means for introducing an A.C. signal across said phosphor and said metallic layers.

2. An indicator panel in accordance with claim l, wherein, said sheet of plastic is made from one of the group of plastics consisting of polyesters, cellulose acetate and acetate butyrate.-

3. An indicator panel in accordancewith claim 1', wherein, at least one edge of said sheet of plastic extends past the first ceramic layer.

4. In an indicator panel for use in providing indications as to the operation of apparatus enclosing the indicator panel,

a layer of electrically insulating material and having first and second opposite surfaces,

a phosphorescent layer disposed on the iirst surface` -of the layer of insulating material,

a layer'of an electrically conductive material disposed on the phosphorescent layer,

a Vfirst electrically conductive lead electrically coupled to the electrically conductive layer and extendin from the electrically conductive layer,

a second electrically conductive lead electrically coupled to the phosphorescent layer and extending from the' phosphorescentV layer,

means coupled to the first and second electrically conVJ ductive leads for producing a voltage difference between the leads to obtain a luminescence of the phosphorescent layer, and Y a transparent sheet of plastic material and means to adhere the sheet of plastic material to the layef of electrically insulating material to strengthen the inJ dicator panel and prevent cracking and with the sheet of plastic material provided with characteristics to obtain a passage through Vsuch sheet of plastic material of the luminescence produced upon the occurrence of the voltage difference between the first and second leads and to obtain a visual display of the luminescence passing through such means upon the occurrence of a relatively low level of light in the space surrounding such sheet of plastic material.

5. In the indicator panel set forth in claim 4 wherein the sheet of plastic material is metallized toobtain the passage through the sheet of the luminescence produced upon the occurrence of the voltage difference between the first and second electrically conductive leads and to obtain the visual display of the luminescence passing 5 6 through the sheet upon the occurrence of the relatively 2,887,402 5/ 1959 Ballard 117-335 10W level of light in the space surrounding the sheet. 2,900,545 8/ 1959 RUIOII et al- 313--108 2,908,806 10/1959 Cohen 240-2.17 References Cited by the Examiner 2,958,762 11/ 1960 Cheney 240-10 UNITED STATES PATENTS 5 3,161,797 12/1964 Butler et al. 313-108 2,716,298 8/ 1955 Spielmann et al 340-132 JAMES W. LAWRENCE, Primary Examiner.

Bouchard et al R. Assistant Examiner. 

1. AN INDICATOR PANEL, INCLUDING, AN ELECTROLUMINESCENT PANEL HAVING A PHOSPHOR LAYER, A METALLIC LAYER HAVING ONE SIDE POSITIONED AGAINST ONE SIDE OF THE PHOSPHOR LAYER, A FIRST TRANSPARENT CERAMIC LAYER AGAINST THE OTHER SIDE OF THE PHOSPHOR LAYER, AND A SECOND TRANSPARENT CERAMIC LAYER AGAINST THE OTHER SIDE OF THE METALLIC LAYER, A METALLIZED VACUUM PLATED FLEXIBLE SHEET OF PLASTIC AGAINST SAID FIRST TRANSPARENT LAYER AND WITH THE SHEET OF PLASTIC INCLUDING INDICIA, MEANS FOR ADHERING SAID SHEET OF PLASTIC TO SAID FIRST CERAMIC LAYER TO PREVENT THE ELECTROLUMINESCENT PANEL FROM CRACKING, AND MEANS FOR INTRODUCING AN A.C. SIGNAL ACROSS SAID PHOSPHOR AND SAID METALLIC LAYERS. 